This invention relates to a catalyst composition useful in the removal of sulfur and nitrogen from gas oils, as practiced in the hydrocarbon refining industry, in a process commonly referred to as hydroprocessing.
A solid catalyst, such as the material provided by the present invention, is contained by a reactor. The material to be hydroprocessed is passed over the catalyst together with a flow of hydrogen, at comparatively moderate temperatures and pressures and flow rates. In customary practice, the catalysts consist of metal oxides on a support, where the oxides are converted to sulfides prior to use to produce an active, stable catalyst. The hydroprocessed product is a gas oil in which the sulfur and nitrogen contents have been substantially reduced. Any improvement of this process, especially as relating to the use of a material having improved activity for catalyzing this reaction, will result in significant economic savings as well as improved yield.
In the catalytic hydroprocessing art, as it is currently practiced, catalysts typically consist of active metals, either molybdenum or tungsten plus either nickel or cobalt, optionally with promoters, on an inert support consisting of alumina, silica or a mixture thereof. The use of different supports, or other active metals, has been found to either enhance or decrease the activity as compared to the base catalyst. Also, varying the method of preparation of these materials can result in a change in catalytic activity.
Hydroprocessing catalysts have traditionally been prepared by depositing aqueous solutions of molybdenum, tungsten, nickel and cobalt salts onto a support, either in separate steps or by co-deposition. Alternately, the support and the deposited metals can be formed simultaneously. Intermediate and final calcining steps are necessary to produce the final form of the catalyst, i.e., an alumina support holding more-or-less dispersed molybdenum, tungsten, nickel and cobalt oxides. Numerous variations in both methods and compositions of this procedure have been described.
These hydroprocessing catalysts can be improved. One method is to use an improved support structure, including improvements in composition and physical structure. A small increase in the cost of the catalyst, which might be incurred by implementing additional process steps in making the improved support structure, can result in significant overall savings, by permitting operation of the hydroprocessing process at less severe conditions or at a higher throughput.
Therefore, it is an object of the present invention to provide an improved catalyst, suitable for use in hydroprocessing, containing molybdenum and nickel on an improved titanium and/or zirconium oxide support.
Moreover, another object of the present invention is to provide a process for the removal of sulfur and nitrogen from hydrocarbon streams, employing the improved hydroprocessing catalyst of this invention.